The cost, C = f(w), in dollars of buying a chemical is a function of the weight bought, w, in pounds.

(a) In the statement f(12) = 5, what are the units of the 12? What are the units of the 5? Explain what this is saying about the cost of buying the chemical.

(b) Do you expect the derivative f' to be positive or negative? Why?
(c) In the statement f'(12) = 0.4, what are the units of the 12?What are the units of the 0.4? Explain what this is saying about the cost of buying the chemical. Figure 2.33 shows world solar energy output, in megawatts, as a function of years since 1990. Estimate f'(6). Give units and interpret your answer.